In sterile bottling of beverages, it is known that the air present in the head space of the beverage container may be displaced, e.g., by introducing liquid nitrogen, as is known from EP 0 481 019 B1, for example. Adding liquid nitrogen largely displaces the total atmospheric oxygen present in the container, thereby achieving better shelf life of the beverage.
In hot bottling of beverages in PET containers, the thermal stability of the material and the vacuum stability of the container also constitute a challenge, which is met through various measures. Because of the low glass transition point of approximately 75° C., the thermal stability of PET is not sufficient for filling temperatures of sensitive products, which are usually bottled in temperature ranges between 85° C. and 92° C. Therefore, the material must usually be thermally crystallized in processing in the stretch blow molding machine. This is implemented by a high temperature of the processed preforms (so-called preform temperature) and heated blow molds (120° C. to 160° C.). However, this results in much higher energy consumption because in these methods, additional cooling of the container by compressed air is necessary before unmolding. Another disadvantage is the limited output performance due to the required crystallization time in the mold.
Compensation for the volume shrinkage of the filling product due to cooling may be implemented by a relatively complex bottle design, such as that known from WO 2006/062829 A2, for example. These bottles, which are suitable for hot bottling containers, are much heavier in comparison with conventional designs for cold bottling containers, are more complex to manufacture, and thus are also much more expensive. However, in view of the high cost of raw materials, which will continue to rise in the future, it is becoming increasingly less economical to achieve the advantages of hot bottling by way of a higher bottle weight. Furthermore, bottles having vacuum equalizing surfaces are more difficult to label and in some cases have a definitely reduced stackability.
For this reason, JP 06 263 190 A describes a method for hot filling of thin-walled containers, in which the container stability after the cooling phase is to be ensured by introducing liquid nitrogen, because its expansion counteracts the shrinkage process due to the cooling of the container contents.